Core for electrical devices



March 17, 1942. 0.. c. PRINCE 2,276,793

CORE FOR ELECTRICAL DEVICES Filed April 50, 1941 l5 MAX/MUM MAG/15m ORIENTATION /0 Inventor: Dav'cl C. Prince,

His Attorney.

Patented Mar. 17, 1942 CORE FOR ELECTRICAL DEVICES David 0. Prince, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application April 30, 1941, Serial No. 391,039

11 Claims.

My invention relates to laminated cores for electrical devices.

In cores for electrical devices such as dynamoelectric machines, in which windings are placed in slots in the surface of the core, the flux in the teeth on the sides of the slots is subjected to high frequency pulsations caused by relative movement of the teeth on the core and teeth on an adjacent core member. These flux pulsations cause a tooth tip core loss which forms a substantial part of the total core loss of such a device. In analyzing the core losses of such devices, attention must be given both to the losses due to eddy currents caused primarily by high frequency pulsations and also to hysteresis losses due primarily to low frequency pulsations. The effect of grain structure on the high frequency core losses is not indicated in Epstein tests, because in this test one-half the iron to be tested is arranged so that flux passes across the grain and the other half of the iron is arranged so that the flux passes with the grain of the material. The directional effect of grain structure, therefore, is not indicated in this test. As the Epstein test is conducted at relatively low frequencies, it does not indicate the losses which would be obtained at high frequencies occurring in the teeth of the core of a device such as a dynamo-electric machine. It has been found that if the grain structure of the steel is not elongated but is more nearly equiaxed, the high frequency tooth tip core losses of laminations are lowered, even though the Epstein test does not indicate that this reduction could be expected. These characteristics of ferro-magnetic materials have been discussed in detail in U. S. Patent 2,053,162 to R. M. Pfalzgraff, assigned to the assignee of this application, and generally may be called the magnetic orientation of the material. This magnetic orientation includes the crystalline arrangement as well as the grain structure.

An object of my invention is to provide improved cores for electrical devices having low core losses and improved magnetic properties.

Further objects and advantages of my invention will become apparent andmy invention will be better understood from the following description referring to the accompanying drawing, and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In the drawing,'Fig. 1 is a fragmentary view of a strip of ferro-magnetic material from which a core of my improved construction may be made; Fig. 2 is an end elevation of a completed core embodying my invention; Fig. 3 is an end view of an edgewise wound helical core embodying my invention; and Fig. 4 is a side view of the core shown in Fig. 3.

Referring to the drawing, Fig. 1 illustrates a strip of ferro-magnetic material comprising two portions Ill and II provided with serrated edges I2 and I3, respectively, which are matched and integrally. connected together by welding along this edge. This method of integrally connecting together two strips of material provides a larger contact surface between the two connected strips and insures better contact therebeween. The methodof thus connecting togetherelements is described and claimed in U. S. Patent 1,773,068 to J. J. Vienneau. In forming ferro-magnetic cores for electrical devices wherein an edge of the core is adapted to be arranged adjacent another ferro-magnetic core member 9 and the other portion of the core is adapted to carry the flux from one part of the core to another, the eddy current and hysteresis losses may be decreased and the magnetic properties improved by arrangingthe strip I I which is adapted to be arranged adjacent the other core member 9 such that the maximum magnetic orientation of the strip II is substantially transverse of the strip,

as shown by the arrows I I, while the maximum magnetic orientation of the material in the strip I0 is substantially longitudinal of the strip, as shown by the arrows I5. This provides core portions having their maximum magnetic orientation substantially in the direction of the flux in the different portions of the core.

In order to form a substantially circular core for a dynamo-electric machine having relatively large diameter, arcuate sectors I6 are punched from a strip such as shown in Fig. 1 and a plurality of teeth I! is punched in an arcuate edge of the portion ll of the sector It. In this manner, the maximum magnetic orientation of the material is substantially longitudinal of the teeth and substantially radial of the arcuate edge of the sector, while the maximum magnetic orientation of the outer portion H) of the core is substantially transverse of the teeth and of the radial direction of the arcuate sector, as shown by the arrows l8 and [9, respectively. A core for the stator of a dynamo-electric machine may be made by assembling a plurality of sectors l6, as shown in Fig. 2, and stacking a number of these laminations to provide continuous slots longitudinally of the stacking. These laminated sectors then may be secured together by suitable bolts or rivets 2i? and retained in assembled re lationshipbetween any suitable end plates. as in conventional machines.

In Figs. 3 and 4, I have shown a modification of the construction shown in Fig. 2, wherein a strip of ferro-magnetic material, such as shown in Fig. l, is formed with a plurality of teeth in an edge of the portion ll having the maximum magnetic orientation substantially transverse thereof and longitudinal of the teeth 2|, as indicated by the arrows ill. Such a strip then is edgewise, wound to form a fine pitch helix from which the teeth extend substantially radially, and a core is obtained in which the maximum magnetic orientation is substantially radial in the toothed portion Ii and is substantially circumferential or the core in the outer portion II), as shown by the arrows iii. The advantage of such an arrangement is that the maximum orientation is substantially in the direction of the flux in thecore, thereby decreasing the eddy current and hysteresis losses and increasing the magnetic properties of the core. This core is retained in assembled relationship by a plurality of rivets or bolts 22. It is thus seen that I utilize the most advantageous arrangement of granular and crystalline structure magnetic orientation of the two portions of the core to-provide the desired improved characteristics thereto.

While I have illustrated and described particular embodiments of my invention, modifications thereof will occur to those skilled in the art. I desire it to be understood, therefore, that my invention is not to be limited to the particular arrangements disclosed, and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

What I claimas new and desire to secure by Letters Patent of the United States is:

1. A core of i'erro-magnetic material for electrical devices including a portion having teeth formed in an edge thereof and comprising material having maximum magnetic orientation substantially longitudinally of said teeth, and a second core portion integrally connected to said toothed portion on the side thereof away from said teeth and comprising material having maximum magnetic orientation substantially transversely of said teeth.

2. A core of ferro-magnetic material including a portion having teeth formed in a substantially arcuate edge thereof and having the opposite edge thereof serrated, said portion comprising material having maximum magnetic orientation substantially radially of said arcuate edge, and

a second core portion having a serrated edge integrally connected to said serrated edge of said toothed portion and comprising material having maximum orientation substantially transversely of said radial direction.

3. A core of ferro-magnetic material for dynamo-electric machines including a portion having teeth formed in a substantially arcuate edge thereof and comprising material having maximum magnetic orientation substantially radially of said arcuate edge. and a second core portion integrally connected to said toothed portion on the side thereof away from said teeth and comprising material having maximum magnetic orientation substantially transversely of said radial direction.

4. A core ferro-magnetic material for electrical devices including a portion having teeth formed in a substantially arcuate edge thereof aavavea and comprising material having maximmn magnetic orientation substantially radially said arcuate edge, and a second core portion having a serrated edge integrally connected to said toothed portion on the side thereof away from said teeth and comprising material having maximum magnetic orientation substantially transversely of said radial direction.

5. A core oi ferro-magnetic material for electrical devices formed of arcuate sectors, each of said sectors including a portion having teeth formed in a substantially arcuate edge thereof and having the opposite edge thereof serrated. said portion comprising material having maximum magnetic orientation substantially radially of said arcuate edge, and a second core portion having a serrated edge integrally connected to said serrated edge of said toothed portion and a substantially arcuate edge opposite said serrated edge, said second core portion comprising material having maximum magnetic orientation substantially transversely of said radial direction.

6. A core for electrical devices comprising a thin strip of ferro-magnetic material in the form of a fine pitch helix formed of two longitudinally extending portions integrally connected together, one 01' saidportions comprising material having maximum magnetic orientation substantially transversely of said strip and the other portion of said strip comprising material having maximum magnetic orientation substantially longitudinally of said strip.

7. A core for electrical devices comprising a thinstrip of ferro-magnetic material in the form of a fine pitch helix formed of two longitudinally extending portions integrally connected together, one of said portions having a-plurality of teeth formed in an edge thereof with teeth in adjacent convolutions of said helix arranged in axial registry and comprising material having maximum magnetic orientation substantially transversely of said strip and the other portion of said strip comprising material having maximum magnetic orientation substantially longitudinally of said strip.

8. A core for electrical devices comprising a thin strip of ferro-magnetic material in the form of a fine pitch helix having an edge thereof adapted to be arranged adjacent another core of magnetic material and being formed of two longitudinally extending portions integrallv connected together, said core strip portion adjacent said core comprising material having maximum mag netic orientation substantially transversely of said strip and the other portion of said core strip comprising material having maximum magnetic orientation substantially longitudinally of said strip.

9. A core for electrical devices comprising a thin strip of term-magnetic material in the form of a fine pitch helix having an edge thereof adapted to be arranged adjacent another core of magnetic material and being formed of two longitudinally extending portions, each of said portions having a serrated edge arranged in engagement with the serrated edge of the other portion and being integrally connected thereto, said core strip portion adjacent said other core comprising material having maximum magnetic orientation substantially transversely of said strip and the other portion of said core strip comprising material having maximum magnetic orientation substantially longitudinally'of said strip.

'10. A core for electrical devices comprising a thin strip of term-magnetic material in the form aeravee Y of a line pitch helix formed of two longitudinally extending portions, each of said portions having a serrated edge arranged in engagement with the serrated edge of the other portion and being integrally connected thereto, one of said portions having a plurality of teeth formed in an edge thereof with teeth in adjacent convolutions of said helix arranged in axial registry and comprising material having maximum magnetic orientation substantially transversely of said strip and the other portion of said strip comprising material having maximum magnetic orientation substantially longitudinally of said strip.

11. A core for dynamo-electric machines comprising a thin strip of term-magnetic material in the form of a fine pitch helix formed with a plurality of teeth in an edge thereof, said teeth being arranged in axial registry in adjacent convolutions, and said strip of term-magnetic material being formed of two longitudinally extending portions integrally connected together, one 

